A 5-HT4 receptor which was a subtype of serotonin receptor has been found in an action mechanism study of metoclopramide [4-amino-5-chloro-N-(2-diethylaminoethyl) -2-methoxybenzamide] which was an enterokinesis-promoting agent or a digestive tract function -improving agent in widespread clinical use. Thereafter, it became clear that an enterokinesis-promotion activity of benzamide derivatives such as metoclopramide or cisapride {cis-4-amino-5-chloro-N-[1-[3-(4-fluorophenoxy)propyl]-3-methoxy-4-piperidinyl]-2-methoxybenzamide} was caused by stimulating 5-HT4 receptors (see Nonpatent Documents 1 and 2). Further, a 5-HT4 receptor agonist tegaserod [2-(5-methoxy-1H-indol-3-ylmethylene)-N-pentylhydrazinecarboxyimidamide] was approved for indications for chronic constipation and constipation-type irritable bowel syndrome in the United States and Europe, and defecation improvement activities by stimulation of 5-HT4 receptors have been verified.
However, metoclopramide has a 5-HT4 receptor agonistic action, while it also has a dopamine D2 receptor antagonism contributing adverse effects which causes central depressant, which has been one of clinical problems. Additionally, the sale of cisapride was stopped due to its adverse effects to the heart, e.g., serious ventricular arrhythmia and QT extension as well as its central depressant action based on a dopamine D2 receptor antagonism. Tegaserod has been temporarily withdrawn from the market of the United States due to its increased risk of serious ischemic cardiovascular adverse effects.
Since patients suffering from digestive system-indefinite complaint tend to be increased, development of excellent enterokinesis-promoting agents or improving agents for digestive tract function with less adverse effects is aspired in clinical practice.
It has been known that morpholine derivatives etc. with benzyl group etc. on nitrogen atom on 4-position among morpholine ring or 1,4-hexahydroxazepine ring compounds have selectively agonistic effects on 5-HT4 receptors, and are useful as an enterokinesis-promoting agent or a digestive tract function-improving agent (see Patent Document 1).
Additionally, it has been known that N-carboxyalkylmorpholine derivatives have a prokinetic effect on digestive tract function and an antiemetic action and are useful as a therapeutic agent for digestive system disease (see Patent Document 2).
Further, it has been known that N-substituted morpholine derivatives etc. have enterokinesis -stimulating properties and accelerate the gastric emptying (see Patent Document 3).
However, a compound wherein a saturated nitrogen-containing heterocycle binds to nitrogen on 4-position in morpholine ring or 1,4-hexahydroxazepine ring via methylene group has not been reported.    Nonpatent Document 1: J. Pharmacol. Exp. Ther., (1990) 252, p 1378    Nonpatent Document 2: J. Pharmacol. Exp. Ther., (1991) 257, p 781    Patent Document 1: European Patent Application Publication No.: 243959    Patent Document 2: WO92/14705    Patent Document 3: WO96/37486